47 lines
1.4 KiB
Go
47 lines
1.4 KiB
Go
// Copyright 2020 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package bls12381
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import (
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"strings"
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"encoding/hex"
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"errors"
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"math/big"
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)
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func bigFromHex(hex string) *big.Int {
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b, _ := hex.DecodeString(strings.TrimPrefix(hex, "0x"))
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return new(big.Int).SetBytes(b)
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}
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// decodeFieldElement expects 64 byte input with zero top 16 bytes,
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// returns lower 48 bytes.
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func decodeFieldElement(in []byte) ([]byte, error) {
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if len(in) != 64 {
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return nil, errors.New("invalid field element length")
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}
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// check top bytes
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for i := 0; i < 16; i++ {
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if in[i] != byte(0x00) {
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return nil, errors.New("invalid field element top bytes")
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}
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}
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out := make([]byte, 48)
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copy(out[:], in[16:])
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return out, nil
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}
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